1. Field of the Invention
This invention relates to transparent recording materials suitable for use in electrography and xerography. Specifically, it relates to coatings for transparencies having specific physical properties for use in overhead projectors.
2. Description of Related Art
In the formation and development of xerographic images, a toner composition comprised of resin particles and pigment particles is generally applied to a latent image generated on a photoconductive member. Thereafter, the image is transferred to a suitable substrate, and affixed there, by the application of heat, pressure, or a combination thereof. It is also known that transparencies can be selected as a receiver for this transferred developed image originating from the photoconductive member. The transparencies are suitable for use with commercially available overhead projectors. Typically, these transparent sheets are comprised of thin films of one or more organic resins such as polyesters which have undesirably poor toner composition adhesion.
Many different types of transparencies are known in the art. They can be made by different printing and imaging methods, such as thermal transfer printing, ink-jet printing and plain paper copying. U.S. Pat. No. 3,535,112 discloses transparencies comprised of a supporting substrate, and polyamide overcoatings. U.S. Pat. No. 3,539,340 discloses transparencies comprised of a supporting substrate and coatings thereover of vinylchloride copolymers. Also known are transparencies with overcoatings of styrene/acrylate, or methacrylate ester copolymers, as discussed in U.S. Pat. No. 4,071,362; transparencies with blends of acrylic polymers and vinyl chloride/vinylacetate polymers, as illustrated in U.S. Pat. No. 4,085,245, and transparencies with coatings of hydrophilic colloids as recited in U.S. Pat. No. 4,259,422. U.S. Pat. No. 4,489,122 discloses transparencies with elastomeric polymers overcoated with poly(vinylacetate), or terpolymers thereof.
U.S. Pat. No. 4,956,223 discloses an ink jet recording medium comprising a recording surface having a characteristic of directional diffuse reflection. The recording medium can be a transparent substrate having an ink-receiving coating thereon. The ink-receiving layer contains pigments such as mica, pearl pigments, and metal powders therein.
Japanese Patent No. 1289838A discloses a composite polyester film having a cover layer comprising a concentration of sulfonic acid or sulfonate on at least one surface. The composite film is taught to eliminate "pile traveling" (simultaneous feeding of more than one sheet), and yield excellent transparency flatness, and easy toner adhesion.
EP 398223A discloses a plastic film comprising a support and an antistatic layer, particularly useful in light-sensitive silver halide photographic materials having excellent antistatic abilities and no haze, even when quickly dried. The film also has no deterioration of antistatic abilities after processing steps such as development. The antistatic layer comprises a reaction product of a water-soluble electroconductive polymer, hydrophobic polymer particles and a curing agent, characterized in that the polymer has a polyalkylene oxide chain.
Japanese Laid-Open Publication 57-42741 discloses an antistatic composition for use with plastics, which can be coated on the surface, adsorbed onto the surface after dilution with an appropriate solvent, or mixed into the plastic composition prior to molding. The antistatic composition contains 5-95 parts anionic surfactant containing a perfluorocarbon chain with a carbon chain length of 4-16, and 5-95 parts of a nonionic surfactant also having a 4-16 carbon containing perfluorocarbon chain.
The final plastic contains 0.01 part to 5 parts of the antistatic composition per 100 parts plastic when cOated or adsorbed and 0.01 to 10 parts per 100 parts plastic when the antistatic composition is premixed with the plastic.
Japanese Laid-Open Publications 84654/1980 and 174541/1986 disclose antistatic layers which comprise a water-soluble electroconductive polymer having a carboxyl group, a hydrophobic polymer having a carboxyl group and a polyfunctional aziridine. It is disclosed that with this method, antistatic ability can remain after developing (photographic), but transparency of the coated film is greatly dependant on the drying speed. The transparency was unusable when fast-drying techniques were used.
U.S. Pat. No. 4,480,003 discloses a transparency film for use in plain paper electrostatic copiers. The base of the transparency film is a flexible, transparent, heat resistant polymeric film. An image receiving layer, preferably, a toner-receptive, thermoplastic, transparent polymethyl methacrylate polymer containing dispersed silica particles is coated on a first major surface of the polymeric film. On the second major surface of the film base is coated a layer of non-migratory electrically conductive material, preferably a polymer derived from the reaction of pyridine and 2 amino-pyridine with partially chloromethylated polystyrene. It is preferred that a primer coating be interposed between the polymeric film base and the layer of conductive material to provide suitable adhesion of the coating to the film base. It is also preferred that the layer of conductive material be over-coated with a protective coating having additives to control abrasion, resistance, roughness and slip properties. It is disclosed that the sheet can be fed smoothly from a stack and produces clear background areas.
U.S. Pat. No. 4,869,955 discloses an element suitable for preparing transparencies using an electrostatic plain paper copier. The element comprises a polyethylene terephthalate support (polyester), at least one subbing layer coated thereon and, coated to the subbing layer, a toner receptive layer comprising a mixture of an acrylate binder, a polymeric antistatic agent having carboxylic acid groups, a crosslinking agent, butylmethacrylate modified polymethacrylate beads and submicron polyethylene beads. These elements produce excellent transparencies.
U.S. Pat. No. 4,956,225 discloses yet another transparency suitable for electrographic and xerographic imaging comprising a polymeric substrate with a toner receptive coating on one surface thereof. The toner receptive coating comprises blends selected from a group consisting of: poly(ethylene oxide) and carboxymethyl cellulose; poly(ethylene oxide), carboxymethyl cellulose and hydroxypropyl cellulose; poly(ethylene oxide) and vinylidene fluoride/hexafluoropropylene copolymer; poly(chloroprene) and poly(alpha-methylstyrene); poly(caprolactone) and poly(alpha-methylstyrene); poly(vinyl isobutylether) and poly(alpha-methylstyrene); poly(caprolactone) and poly (.alpha.-methylstyrene); chlorinated poly(propylene) and poly(.alpha.-methylstyrene); chlorinated poly(ethylene) and poly(.alpha.-methylstyrene); and chlorinated rubber and poly(.alpha.-methylstyrene). Also disclosed are transparencies with first and second coating layers.
EP Application 0349,227 discloses a transparent laminate film for full color image-forming comprising two transparent resin layers. The first resin layer is heat-resistant, and the second resin layer must be compatible with a binder resin constituting the toner to be used for color image formation. The second resin layer has a larger elasticity than that of the binder resin of the toner at a fixing temperature of the toner. The second resin can be of the same "kind" i.e., type, e.g., styrene-type or polyester type, as the toner binder, as long as the resins differ in storage elasticity.
EP 408197A2 discloses an imageable copy film comprising a thermoplastic polymeric film substrate with a widthwise thermal expansion of 0.01 to 1% at 150.degree. C. and a lengthwise thermal shrinkage in the film of 0.4 to 2.0% at 150.degree. C. The substrate has a receiving layer on at least one surface thereof comprising an acrylic and/or methacrylic resin comprising any film-forming resin, e.g., polymers derived from alkyl esters having up to 10 carbon atoms, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, hexyl, 2-ethylhexyl, heptyl and n-octyl. The use of ethylacrylate or butylacrylate together with an alkylmethacrylate is preferred. Other suitable monomers include acrylonitrile, methacrylonitrile, halo substituted acrylonitrile and (meth)acrylonitrile, acrylamide, methacrylamide, n-methylol acrylamide and methacrylamide, n-ethanol acrylamide and methacrylamide, n-propanol acrylamide and methacrylamide, t-butylacrylamide, hydroxyl ethylacrylamide, glycidyl acrylate, and methacrylate, dimethylamino ethyl methacrylate, itaconic anhydride and half ester of itaconic acid. Vinyl monomers such as vinylacetate, vinylchloroacetate, vinyl benzene, vinyl pyridine, vinyl chloride, vinylidene chloride, maleic acid, maleic anhydride, styrene and substituted styrene, and the like can optionally be included.
EP 442567A2 discloses a medium for electrophotographic printing or copying comprising a polymeric substrate coated with a polymeric coating having a Tukon hardness of about 0.5 to 5.0 and a glass transition temperature of about 5.degree. to 45.degree. C. The coating comprises at least one pigment which provides a coefficient of static friction of from 0.20 to 0.80 and a coefficient of dynamic friction of from 0.10 to 0.40. The medium has improved image quality and toner adhesion. It is particularly useful in laser electrophotographic printing. The polymer employed in the coating can contain thermosetting or thermoplastic resins, and preferably aqueous acrylic emulsions such as Rhoplex.TM. resins from Rohm and Haas.
U.S. Pat. No. 5,104,731 discloses a dry toner imaging film media having good toner affinity, anti-static properties, embossing resistance and good feedability through electrophotographic copies and printers. The media comprises a suitable polymeric substrate with an antistatic matrix layer coated thereon. The matrix layer has resistance to blocking at 78.degree. C. after 30 minutes and a surface resistivity of from about 1.times.10.sup.8 to about 1.times.10.sup.14 ohms per square at 20.degree. C. and 50% relative humidity. The matrix contains one or more thermoplastic polymers having a T.sub.g of 5.degree. C. to 75.degree. C., and at least one crosslinked polymer which is resistant to hot roll fuser embossing, at least one of the polymers being electrically conductive.
Although there are a host of recording sheets available for use, as illustrated by the prior art, there remains a need for new recording sheets having coatings that will enable the formation of images with high optical densities, good feedability, low haze and excellent toner adhesion, especially for use with high speed copiers.
While toner adhesion problems can be eliminated if one uses similar types of binder resin both for the toner and recording sheet coating, as discussed in EP 0349,227 above, that means the coating for the recording sheets has to be changed every time a different toner resin is used. Also, some of these toner resins are only be feasible in solvent-based coatings, as disclosed in EP 0349,227.
The present inventors have now discovered a class of polymers that can be coated in an aqueous medium to produce a transparency image on various copiers using a variety of toners with different binder resins, with excellent adhesion, good image quality and good feedability.